Lithopone-white and process of treating same.



CARL RUDOLF STEINAU', OF NUREMBERG, GERMANY.

LI'IHOPONE-WHITE AND PROCESS FOR TREATING SAME.

No Drawing.

Specification of Letters Patent. Application filed Apri1 27, 1907. Serial No. 370,700.

Patented Apr; 26, 1910.

To all whom it may concern: I

Be it known that I CARL RUDOLF STEINAU, a subject of the (iterman Emperor, and a resident of Nuremberg, Germany, haveinvented a certain new and useful Improvement in Lithopone-White and Procof zinc or magnesium,

esses for Treatin Same, of which the following is a specification.

Itis well known that all commercial lithopone whites as now manufactured, blacken or at least become gray, when exposed to the action of the atmosphere and sunli ht. While many theories have been advance to account for this property of lithopone, the most plausible theory appears to be that such b ackening is caused by the resence in the. lithopone of zinc chlorld an cadmium .chlorid. These compounds are formed during the heating in the manufacture of the product, asa result of the action of the chlorids of sodium or barium on the zinc or cadmium salts, the chlorids named being commonly added as adulterants.

The object of my invention therefore, is the provision of a process by which the lithopone is so treated that it resists perfectly the action of sunlight and'the atmosphere, and will retain its white color.

y new process consists in treating-the lithopone white, formed in the ordinary well known manner, with metallic carbonates easily yielding their carbonic acid, and with a suitable salt easily absorbing chlorin and oxygen. I have found that among other chemica s carbonate of magnesia combined with an alkaline earth nitrite or a nitrite is exceedingly efiicient for this purpose and that also zinc-carbonate with metal oxids will produce good results. Magnesium carbonate or zinc carbonate used alone would not allow of the attainment'of my purpose, but the addition of one of the nitrltes mentioned, without the carbonate, furnishes a lithopone white resistin to an extraordinary degree the action 0 light. The addition of the carbonates, however, renders the action of the nitrites perfectly effective. The best results are obtained in the following manner: 100 parts of annealed and ground lithopone are treated in water with} to 5 partsof an alkaline earth or other nitrite as above mentioned and a similar amount of carbonate of magnesia at ordinary atmospheric tem erature from 12 to 24 hours, or they are oiled by means of The mixture is then heate direct steam during 1 to 5 hours and longer while theliquid is continuously stirred; or they may be kneaded to ether at ordinary temperatures with a litt e water so as to .form a homogeneous paste, which is then dried andground. When operating the dry process 100 parts of lithopone as ordinarily found in commerce, is mixed with a} to 5 parts of the alkaline earth orothernitrite and a similar. amount of carbonate of mag nesia.

The process is also suitable for lithopone containing calcium compounds.

In order to carryout one form of my process, the ordinary lithopone of commerce is converted into a paste by means of water and thorou hly mixed with from .3 to 5 per cent. of ni rite of barium, nitrite of magnesium, nitrite of zinc or the like alone or in combination with to 5 per cent. of carbonate of magnesium, carbonate of zinc or the like.

The quantities or percentage may be greater or less according to requirements.-

1 to 5 hours,'and is then dried or treated at by steam during the ordinary temperature during a c0rrespondingly longer space-of time that is to say 12 to 24 hours, and then dried. Or if desired lithopone in a dry state may be mixed with the desired nitrite, then mixed with carbonate of magnesia to which a little water has becn added, and the resultant mixture dried and pulverized. When so made the resultant powder may be readily prepared for practical purposes 1n any quantities desired. v

-I am aware that the s ecification of the British Patent No. 7819 of discloses a process according to which lithopone affected by the action of the light, is treated with those neutral salts of potas sium and sodium cipitate zinc from solutions of its salts. The nitrites of the metals mentioned are however such neutral salts as are not capable of pre ci itatin zinc from the solutions of its .sa ts. T e carbonates of magnesia and of zinc which I use,.are neither compounds which are soluble in water, nor are they adapted to precipitate zinc from the solutions of its salts. They only act as agglomerating agents against the hygroscopic properties of the nitrites which are used in my process.

Having now fully descrlbed my said-1n- March 31st, 1906,

which are adapted to prewhich comprises vention what I claim and desire tov secure by Letters Patent is: b 1. A process for treating lithopone white, which comprises, treating the same with a nitrite of a metal. Y

2..A process for treating lithopone white,

' treating the same with *a nitrite of a relatively (light metal.

3. A process for treating lithopone white, which comprises treating the same with a nitrite of a relatively light metal and a carbonate of a metal.

4. Aprocess for treating lithopone white,

. which comprises treating the same with an alkaline earth nitrite and a metallic carbonate. D

,5. A process for treating lithopone white,

'.which comprises treating the same with an nitrite and analkaline earth alkaline earth carbonate.

substantially as 6. A process for treating lithopone white, which comprises treating the same with magnesium nitrite and magnesium carbonate.

7. A process for treating lithopone white,

which comprises treating the same with magn esium nitrite and magnesium carbonate in the presence of water;

8. A process for treating lithopone white,

which consists in adding 1 -6 parts magnesinm nitrite and 5-5 parts magnesium carbonate to 100 parts lithopone white, adding Water to the mixture, and heating the same, described.

In testimony whereof I have hereunto set my hand in presence of two witnesses.

CARL RUDOLF STEINAU. Witnesses:

Bmmnn FUCHS, HERMANN ,DOEHLEMANN. 

